The present invention relates to the use of resins in subterranean applications, and more particularly, to the use of single component resin systems to strengthen structural features in subterranean formations.
Oil or gas is naturally occurring in certain subterranean formations. A subterranean formation having sufficient porosity and permeability to store and transmit fluids is referred to as a reservoir. A subterranean formation that is a reservoir for oil or gas may be located under land or under a seabed offshore. Oil or gas reservoirs are typically located in the range of a few hundred feet (shallow reservoirs) to a few tens of thousands of feet (ultra-deep reservoirs) below the ground or seabed.
In order to produce oil or gas, a wellbore is drilled into a subterranean formation that is an oil or gas reservoir. A wellbore can be cased or uncased (openhole). A wellbore can have vertical and horizontal portions, and it can be straight, curved, or branched.
Various types of treatments are commonly performed on wells or subterranean formations penetrated by wells. For example, stimulation is a type of treatment performed on a subterranean formation to restore or enhance the productivity of oil or gas from the subterranean formation. Stimulation treatments fall into two main groups: hydraulic fracturing and matrix treatments. In hydraulic fracturing treatments, a viscous fracturing fluid, which also functions as a carrier fluid, is pumped into a portion of a subterranean formation at a rate and pressure such that the subterranean formation breaks down and one or more fractures are created or enhanced. Typically, particulate solids, such as graded sand, are suspended in a portion of the fracturing fluid and then deposited in the fractures. These particulate solids, or proppant particulates, serve to prevent the fractures from fully closing once the hydraulic pressure is removed. By keeping the fracture from fully closing, the proppant particulates aid in forming conductive paths through which fluids may flow.
Matrix treatments are performed below the fracture pressure of a subterranean formation. Matrix treatments can include, for example, treatments to consolidate a matrix of unconsolidated rock particles so that less particulates are produced with the produced hydrocarbon.
Occasionally, formation fines and/or other unconsolidated particulates placed in the subterranean formation during a fracturing, gravel packing, or frac-pack operation may migrate out of the subterranean formation into a well bore and/or may be produced with the oil, gas, water, and/or other fluids produced by the well. The presence of such particulates, whether they are indigenous or added to the subterranean formation, in produced fluids is undesirable in that the particulates may abrade pumping and other producing equipment and/or reduce the production of desired fluids from the well. Moreover, particulates that have migrated into a well bore (e.g., inside the casing and/or perforations in a cased hole), among other things, may clog portions of the well bore, hindering the production of desired fluids from the well. The term “unconsolidated particulates,” and derivatives thereof, is defined herein to include loose particulates and particulates bonded with insufficient bond strength to withstand the forces created by the production of fluids through the formation. Unconsolidated particulates may comprise, among other things, sand, gravel, fines and/or proppant particulates in the subterranean formation.
One technique used in formation consolidation, fines migration control, or other methods to control unconsolidated particulates has been to coat the particulates with a curable resin prior to their introduction into the subterranean formation and allowing the resin to consolidate the particulates once inside the formation. In general, the resin enhances the grain-to-grain, or grain-to-formation, contact between particulates and/or subterranean formation so that the particulates are stabilized, locked in place, or at least partially immobilized such that they are resistant to flowing with produced or injected fluids.
Another method used to control particulate matter in unconsolidated formations involves consolidating unconsolidated subterranean producing zones into hard permeable masses by preflushing the formation, applying a hardenable resin composition, applying a spacer fluid, applying an external catalyst to cause the resin to set, and applying an afterflush fluid to remove excess resin from the pore spaces of the zones. Such multiple-component applications, however, may be problematic. For example, when an insufficient amount of spacer fluid is used between the application of the hardenable resin and the application of the external catalyst, the resin may come into contact with the external catalyst in the well bore itself rather than in the unconsolidated subterranean producing zone. When resin is contacted with an external catalyst an exothermic reaction occurs that may result in rapid polymerization. The polymerization may damage the formation by plugging the pore channels, may halt pumping when the well bore is plugged with solid material, or may even result in a downhole explosion as a result of the heat of polymerization.
In addition, when using conventional resin systems, equipment used in the wellbore may come in accidental contact with the resin. If the curing agent has been added to the resin, the mixture begins to cure on the equipment, causing the equipment to become coated with the cured resin. As a result, the equipments requires extensive cleaning before further use, thereby resulting in increased cost from cleaning and delay in operations. Likewise, using these conventional processes to treat long intervals of unconsolidated regions is often not practical due to the difficulty in determining if the entire interval has been treated with both the resin and the catalyst. Also, the temperature of the subterranean formation may hamper the ability of the hardenable resin to cure. Hence, multiple hardenable resins may be needed depending on the subterranean formation's temperature at the region being treated.
In addition, often times during field operations, the components may be mixed, but then unforeseen circumstances arise that prevent the mixture to be pumped down hole. In these situations, the mixture hardens and is unusable, leading to higher costs. because the hardened mixture must then be discarded, and a fresh batch of resin must be made.